1. Field of the Invention
The present invention relates to a transmission for a vehicle including a parking gear.
2. Description of the Related Art
In an automatic transmission of a vehicle (automobile), there is a transmission referred to as a double clutch (also referred to as twin clutch or dual clutch) transmission for changing speed continuously while restraining a loss of a power by using a normal mesh type gear mechanism in which a drive gear and a driven gear are normally brought in mesh with each other.
In a vehicle including an automatic transmission, inside of the transmission is provided with a parking gear and a claw member arranged at a vicinity of an outer periphery of the drive gear to be able to be engaged with and disengaged from the parking gear at inside of the transmission such that the vehicle is prevented from moving unpreparedly in a state of parking the vehicle and the vehicle is prevented from being moved unpreparedly in a parking state by engaging a front end of the claw member with the parking gear.
Recently, there is known a structure of integrating a parking gear between driven gears of an output shaft such that an excessive torque (caused by a vehicle weight when parked at an inclined location) is prevented from being applied to the parking gear. For example, as disclosed in JP-A-2006-52832, it is described that in a transmission constituting a forward speed changing stage by 6 stages, constituting a rearward speed changing stage by 1 stage, distributing three driven gears of 5 speed, 6 speed, reverse to a first output shaft, and distributing four driven gears of 1 speed, 2 speed, 3 speed, 4 speed to a second output shaft and providing a parking gear between the driven gears of the second output shaft, for example, between the driven gear of 3 speed and the driven gear of 4 speed.
However, according to the transmission of the above-described example, in providing the parking gear at the output shaft, the parking gear is arranged at the output shaft in series with other gear, and therefore, there poses a problem that the output shaft is prolonged and an axial direction length of the transmission is prolonged. Hence, the inventors of the application have investigated to shorten the axial direction length by arranging the parking gear at a well-known synchronizer sleeve for connecting the driven gear to the output shaft to drive. Generally, the synchronizer sleeve is constituted so as not to move in the axial direction unless a predetermined or larger force is exerted in the axial direction by a well-known detent mechanism. However, when the parking gear is provided to the synchronizer sleeve, there is a rare case in which an operating force in engaging a claw member with the parking gear exceeds a restricting force by the detent mechanism from a positional relationship between the parking gear and the claw member and a behavior of the synchronizer sleeve becomes unstable. When the synchronizer sleeve is assumedly moved in the axial direction, also a position of the parking gear is moved and there is a concern that the engagement with the claw member becomes unstable.
Further, in a vehicle of FF (front engine front drive) type, a front portion of the vehicle is integrated with an engine, a transmission, a drive mechanism, a steering mechanism and the like, further, in a transversely placed engine, the engine is provided between tires, side members or the like, and therefore, it is required that a length in the axial direction of the transmission to be as short as possible.